Abstract

Geomorphological, geophysical, archaeological and documentary investigations have been employed to establish the variation of sea level change, sediment supply and geological control from the Late-Holocene, through the Historical period to the Present day, in Sanday. Techniques such as Ground-Penetrating Radar and geomorphological Radar and geomorphological surveying have identified a suite of gravel ridge recurves and placed them within their geomorphological context. The provisional regional sea level curve has been updated and clarified following the discovery and successful dating of a submerged forest. This sea level curve was then used to constrain the development of the coast of Sanday into separate time period. A range of archaeological and historical evidence also informed and corroborated the geomorphological evidence to allow the island’s coastal development to be established over the last few thousand years towards the present day, where differential-GPS and sonar techniques allowed these long-term trends to be placed into their modern context. Island-building occurred during Holocene submergence along with other radical changes to the shape and form of the coastline, all reflecting the changing dominance between the three controlling factors. The accepted outcome of submergence is transgression and fragmentation of islands rather than island building and this is wholly a result of a healthy sediment supply at the early stages. However, this sediment source has since begun to diminish and fragmentation, erosion and transgression may well be the outcome of the present trends in Sanday. This coastal change scenario has been projected forward, using climate change scenarios, to raise significant questions not only for Sanday and those regions which have historically experienced submergence, but also for those areas which previously experienced emergence and more recently are starting to be affected by relative sea level rise